KR20060016808A - Optical communication system with suppressed sbs - Google Patents

Abstract

An optical communication system and a communication network are disclosed herein capable of transmitting optical signals with high optical launch power over long distances. A method of transmitting optical signals is also disclosed herein which comprises transmitting optical signals at high optical launch power with a high CNR and low CTB and CSO.

Description

Optical communication system with suppressed SOS {OPTICAL COMMUNICATION SYSTEM WITH SUPPRESSED SBS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical communication systems, and more particularly to optical fiber transmission systems capable of transmitting wideband signals over single mode optical fibers using high optical oscillation power.

Economical distribution of broadband signal content (such as multichannel cable TV) through single mode fiber optic systems requires the use of high optical signal power. High optical signal power enables splitting of optical signals for distribution over multiple fiber paths, such as representing long distance transmission, or for the alternative transmission of signals over a single fiber path with large link loss. The availability of effective erbium doped fiber amplifiers (EDFA) operating in the 1550 nm wavelength region where standard telecommunication fibers exhibit their minimum attenuation has facilitated the development of broadband transmitters that are compatible with the gain bandwidth of EDFA. However, the standard information communication single mode fiber (for example, Corning SMF-28 ^® fiber) is to represent the variance (dispersion) in the 1550nm region, which is modulated distributed feedback laser (DFB) directly as a transmitter for cable television or high bit-rate digital signal Interfere with use. Instead, a typical transmitter operating at 1550 nm includes a narrow linewidth externally modulated continuous wave (cw) DFB laser. The DFB laser light beam does not carry a signal containing information until an external modulation acts on the laser light beam to represent a signal containing information therein. "Light" here is not limited to the visible spectrum. Optical power is amplified by EDFA downstream from an external modulator. Therefore, the optical signal including the information is input to the optical fiber span at the optical signal power determined by the saturation output power of the EDFA. Commercially available EDFAs provide saturation output power in excess of 20dBm.

As noted, stimulated Brillouin scattering (SBS) is a nonlinear optical effect that places significant limitations on the amount of narrow linewidth optical power that can be input into long mode single mode optical fibers. For a single mode fiber of a given length with a given attenuation coefficient at a selected light wavelength, below that there is a critical power that depends on the optical line width where no distinct SBS occurs. For a standard commercial telecommunication fiber operating at 1550 nm, the SBS threshold for an optical source (laser) with an optical line width of less than 10 MHz is less than 7 dBm for an optical link about 50 km long.

Earlier, to launch high fiber power in the 1550 nm wavelength region for transmission of wideband signals such as cable television over long fiber lengths, SBS must be suppressed. SBS reduces the received optical power by generating excessive noise in the received signal, causing distortion, in particular synthetic secondary distortion, and causing power-dependent nonlinear attenuation in the fiber optic link.

Hybrid multichannel AM-VSB and M-ary quadrature amplitude modulation (M-QAM) subcarrier-multiplexing video lightwave transmission systems are promising technologies for simultaneous transmission of analog video and digital video / data services, both in the telecommunication and cable industries. Is currently under consideration. Within the 50-860 MHz bandwidth, these systems can carry up to about 134 channels of typical broadcast AM-VSB signals and up to 30 channels of M-QAM digital signals using a single laser transmitter simultaneously. Due to the fact that digital signals are stronger against noise and nonlinear distortion, the operating point of such a hybrid system is heavily dependent on the stringent carrier-to-noise ratio (CNR) requirements of the AM channel. The analog part is also limited by nonlinear distortion, in particular second and third order distortions, characterized by CSO and CTB. In order to maintain an acceptable CNR, the power supply of video lightwave systems based on DFB laser transmitters has typically been limited to about 10 dB. This reasonable power margin imposes an upper limit on the number of optical splits and the link length. Applications such as long distance video supertrunking and cable TV distribution and access architectures require higher power supplies. One practical solution for boosting link supply is to use EDFA with a 1550nm DFB laser transmitter. However, adding additional EDFAs can add significant system cost.

Summary of the Invention

An optical communication system is described that can transmit optical signals over a greater distance and / or use higher optical oscillation power than previously thought possible while maintaining acceptable levels of CNR, CSO and CTB. . This system is particularly advantageous for, but not limited to, cable TV and hybrid coaxial fiber cable systems for distribution networks and access networks. The system preferably uses single mode fibers with a high SBS threshold. The system preferably includes a point-to-multipoint optical network for transmitting the optical signal, more preferably for transmitting and receiving the optical signal. The system enables longer optical path distances and / or higher optical oscillation power from the optical signal source to the receiver.

Operation in the sub-carrier multiplexing ("SCM") signal format is particularly suitable for all embodiments described herein. Preferably, the signal under the SCM signal format has an analog component.

As used herein, the output power of the optical signal source is the input power to the associated optical fiber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, with reference to the accompanying drawings, a detailed description of preferred embodiments of the present invention will be described. An exemplary embodiment of a partitioned core refractive index profile according to the present invention is shown in each figure.

1 is a schematic illustration of a telecommunications network useful for cable TV or hybrid coaxial fiber cable networks.

2 is a schematic diagram of the relative refractive index of an optical fiber suitable for use as described herein.

FIG. 3 is a graph depicting SBS thresholds for fiber lengths of optical fibers suitable for use as described herein. FIG.

4 shows the reflected power measured as a function of input power for three optical fibers having a length of about 50 km.

Additional features and advantages of the invention will be set forth in the following description, and from this description will become apparent to those of ordinary skill in the art, as set forth in the following description together with the appended claims and drawings. It will be understood by practicing the invention as such.

The "refractive index profile" is the relationship between the refractive index or relative refractive index and the waveguide fiber radius.

로 정의되고, 여기서 n_i는, 달 리 특정되지 않는다면, 영역 i에서의 최대 굴절률이고, n_c는 클래딩 영역의 평균 굴절률이다. 환상 영역 또는 한 세그먼트의 굴절률이 클래딩 영역의 평균 굴절률보다 작은 경우, 상대 굴절률 퍼센트는 네거티브가 되고, 억제 영역(depressed region) 또는 억제 지수(depressed index)를 갖는다고 말하며, 달리 특정되지 않는다면 상대 지수가 가장 네거티브인 점에서 계산된다. "Relative refractive index"

Where n _i is the maximum refractive index in region i, unless otherwise specified, and n _c is the average refractive index of the cladding region. If the refractive index of the annular region or one segment is less than the average refractive index of the cladding region, the relative refractive index percentage becomes negative and is said to have a depressed region or a depressed index, unless otherwise specified, Calculated at the most negative point.

Unless stated otherwise, the "Chromatic dispersion" of waveguide fibers referred to herein as "dispersion" is the sum of material dispersion, waveguide dispersion, and inter-modal dispersion. In the case of single mode waveguide fibers, the intermodal dispersion is zero. The zero dispersion wavelength corresponds to the wavelength where the dispersion has a value of zero.

로 정의되고, 여기서, 적분 범위는 0 내지 ∞이고, E는 도파관에서 전파된 빛과 관련된 전계이다."Effective area" means

Where the integral range is 0 to ∞, and E is the electric field associated with the light propagated in the waveguide.

이고, 적분 범위는 0 내지 ∞이다.The mode field diameter (MFD) is measured using the Peterman II method, where 2w = MFD,

And an integration range is 0 to ∞.

 Bend resistance of the waveguide fiber can be measured by attenuation induced under specified test conditions.

A "pin array" bend test is used to compare the relative resistance of waveguide fibers to bending. To perform this test, the attenuation loss for the waveguide fiber is measured without the necessary induced bending loss. The waveguide fibers are then woven against the array of fins and the attenuation is measured again. The loss induced by bending is the difference between the two measured attenuations. The pin array is a set of ten cylindrical pins arranged in one row and held in a fixed vertical position on a flat surface. The distance between the centers of the pins is 5 mm. The pin diameter is 0.67 mm. During the test, sufficient tension is applied to match the waveguide fiber to a portion of the fin surface.

The theoretical fiber cutoff wavelength, or “theoretical fiber cutoff” or “theoretical cutoff” for a given mode is the wavelength at which no more induced light can propagate in that mode. The mathematical definition can be found in Single Mode Fiber Optics (Jeunhomme, pp. 39-44, Marcel Dekker, New York, 1990), where the theoretical fiber cutoff is such that the mode propagation constant is equal to the planar wavelength propagation constant in the outer cladding. It is described by the wavelength. This theoretical wavelength is suitable for infinitely long, completely straight fibers with no change in diameter.

Due to the losses caused by bending and / or physical pressure, the effective fiber cutoff is smaller than the theoretical cutoff. In this context, cutoff refers to higher LP11 and LP02 modes. LP11 and LP02 are generally indistinguishable in measurements, but both are evident as steps in spectral measurements. That is, no power is observed in the mode at wavelengths longer than the measured cutoff. The actual fiber cutoff can be measured by the standard 2m fiber cutoff test FOTP-80 (EIA-TIA-455-80) to yield a "fiber cutoff wavelength", known as "2m fiber cutoff" or "measured cutoff". have. The FOTP-80 standard test is performed to break down higher rank modes using controlled amounts of bending, or to normalize the spectral response of the fiber to the spectral response of the multimode fiber.

The cable cutoff wavelength or "cabled cutoff" is much lower than the measured fiber cutoff due to the high level of bending and physical pressure in the cable environment. The actual wireline conditions can be approximated by the cable cutoff test described in the EIA-445 fiber optic test procedure, which is part of the EIA-TIA fiber standard, commonly known as FOTP. Cable cutoff measurements are described in EIA-455-170 cable cutoff wavelength or "FOTP-170" of single mode fibers by transmit power.

As used herein, an optical waveguide fiber link includes one optical fiber or multiple optical fibers, optical fiber cables, or multiple optical fiber cables. Fiber optic cables include one or more optical fibers. The optical signal transmitted through the optical fiber is transmitted through the associated optical fiber path length. The length of the waveguide fiber may consist of many shorter lengths that are glued or connected together in an end-to-end serial arrangement. The link may include additional optical elements such as an optical amplifier, optical attenuator, optical isolator, optical switch, optical filter or multiplexing or demultiplexing device. In a preferred embodiment described herein, the optical fiber link consists of an optical fiber or fiber optic cable that does not use active elements. As described herein, the optical fiber link consists of an optical fiber or fiber optic cable.

Carrier to Noise Ratio (CNR) is the ratio of carrier power to average noise power, measured in decibels (dBc), measured in the 4 MHz bandwidth for channels in the 45–560 MHz range.

Composite Second Order (CSO) is the ratio of the collective distortion signal peak power found at ± 0.75 MHz and ± 1.25 MHz from the carrier frequency to the channel carrier power. This distortion is caused by the secondary nonlinear shape in the transmission system. This is often given in decibels (-dBc) below the carrier of the channel measured as the distortion power synthesis function for the carrier, which is used here.

Composite Triple Beat (CTB) is the ratio (decibels) of the peaks of the collective distortion signal found at the carrier frequency to carrier power. This distortion is created by third order nonlinearity in the transmission system, where it is described as -dBc.

Unless stated otherwise, CNR, CSO, and CTB are measured for channels in the 45-560 MHz range.

1 schematically illustrates a communication network 10 that may be used in a communication system. The communication network 10 shown in FIG. 1 includes, in the illustrated embodiment, an optical transmitter 12 composed of a distributed feedback laser 14, an external modulator 16 and an erbium-doped amplifier 18. The optical transmitter 12 transmits the optical signal to the fiber range 20. The optical signal source is not limited to this form and may be substituted for any one that can transmit the optical signal. Also, although the radio frequency signal generator 19 and the predistortion circuit 21 are not shown, they are not necessary. In the embodiment shown in FIG. 1, the optical fiber span 20 consists of an optical fiber of a first length constituting an optical fiber link 22. The optical fiber link 22 selectively couples the optical signal to a first optical amplifier (eg, EDFA). The second length of optical fiber constitutes the optical fiber link 26, which optically connects the first amplifier 24 to the second optical amplifier 28. The third length of optical fiber constitutes the optical fiber link 30, which connects the second amplifier 28 to the receiver 32. As used herein, fiber link refers to an optical fiber, such as connecting a signal source to an amplifier, a first amplifier to a second amplifier, or an amplifier to a receiver. Fiber optic span 20 includes all fiber links between optical transmitter 12 and receiver 32. Thus, in the embodiment shown in FIG. 1, the combined lengths of the optical fiber links 22, 26, 30 constitute the length of the optical fiber span 20. The fibers that make up each link 22, 26, 30 preferably have the same fiber type.

Although an amplifier is shown in the embodiment shown in FIG. 1, it will be understood that such an amplifier is not necessary in the various embodiments described herein.

The receiver 30 may then be connected to one or more fiber optic links, or alternatively one or more coaxial cable links, and then to an end user downstream. The end user may be an apartment building office or an individual house.

SBS in the optical distribution network 16 can be suppressed by using optical fibers such as those described in US Pat. No. 6,490,396 and US App. No. 60 / 467,676 or 60 / 546,490. In particular, the implementation of such fibers in the fiber span 20 enhances SBS suppression. In a preferred embodiment, all the optical fibers in the optical fiber span 20 have the same optical fiber type. The relative refractive index of this preferred optical fiber that can be used is shown schematically in FIG. 2, which corresponds to FIG. 6 (A-B-C-D) of US Pat. No. 6,490,396. The use of such optical fibers enables higher optical oscillation power into the optical distribution network 16 and enables optical fiber spans 20 with larger optical path lengths than would have been possible without causing SBS signal degradation. do. For example, if an optical fiber or optical cable is at least partially wound or folded or otherwise does not extend all the way in a straight line, for example, from the source to the receiver, the optical fiber path length is such that the signal source and receiver are separated by this. This may be different from the actual physical distance.

The optical fiber shown in FIG. 2 guides a number of acoustic modes including at least one optical mode and L ₀₁ acoustic mode and L ₀₂ acoustic mode. The optical fiber includes a core having a refractive index profile and a centerline and a cladding layer immediately adjacent the core. In a preferred embodiment, the core segment comprises a single core segment having a refractive index profile that is substantially continuously reduced. The effective area of the optical mode of this fiber at 1550nm is greater than 70㎛ ^2, and is greater than ² 80㎛ more preferably, it is greater than 90㎛ ² are most preferred. L ₀₁ acoustic mode is not less than ² 140㎛ in Brillouin frequency of the optical fiber, preferably not less than 150㎛ ^2, more preferably not less than the first acoustic 160㎛ optical effective region ² (acousto-optic effective area ) has a AOEA _L01, L ₀₂ acoustic mode is not less than ² 140㎛ in Brillouin frequency of the optical fiber, preferably not less than 150㎛ ^2, more preferably the second acousto-optic effective area not less than ² 160㎛ AOEA _L02 . The relationship between the L ₀₁ and L ₀₂ acoustic effective areas of the fiber is 0.4 <AOEA _L01 / AOEA _L02 <2.5.

It is preferable that the relative refractive index of the core lies between the upper limit curve and the lower limit curve. The upper curve is a straight line defined by at least two points including a first upper point having a Δ of 0.6% at a radius of 0 and a second upper point having a Δ of 0% at a radius of 14.25 μm. The lower limit curve is a straight line defined by at least two points including a first lower point having a Δ of 0 to 0.25% and a second lower point having a Δ of 0% at a radius of 6 μm.

More preferably AOEA _L01 and _L02 AOEA is not less than ² 180㎛ in Brillouin frequency of the optical fiber, and it is more preferable AOEA _L01 and _L02 AOEA is not less than ² 190㎛ in Brillouin frequency of the optical fiber.

The optical fiber preferably exhibits a zero dispersion (or dispersion 0 or λ ₀ ) wavelength of less than 1480 nm, more preferably 1400 nm, most preferably 1340 nm.

In another preferred embodiment, the optical fiber has zero dispersion at wavelengths below 1320 nm, more preferably between 1290 and 1320 nm.

Preferably, the optical fiber has a dispersion between 15 and 21 ps / nm-km at a wavelength of 1550 nm. In some preferred embodiments, the optical fiber has a dispersion between 16 and 18 ps / nm-km at a wavelength of 1550 nm. In another preferred embodiment, the optical fiber has a dispersion between 18 and 20 ps / nm-km at a wavelength of 1550 nm.

In a preferred embodiment, the optical fiber has a light effective area at 1550 nm greater than 95 μm ² . In another preferred embodiment, the optical fiber has a light effective area of greater than 100 μm ² .

Preferably, the optical fiber has a fin array bending loss at 1550 nm that is less than 15 dB, more preferably 10 dB.

In some preferred embodiments, the upper curve is a straight line defined by at least two points including a first upper point having a Δ of 0.5% at a radius of 0 and a second upper point having a Δ of 0% at a radius of 11.25 μm.

In a preferred embodiment, the core comprises a first portion extending at a radius of 1 μm in the centerline, the first portion having a relative refractive index greater than 0.25% and less than 0.5%.

Preferably, dΔ / dR> −0.15% μm for all radii from r = 0 to r = 1. Preferably, the absolute value of the difference between Δ (r = 0 μm) and Δ (r = 1 μm) is less than 0.1%.

The core also preferably includes a second portion enclosed immediately adjacent to the first portion, which extends to a radius of 2.5 μm and has a Δ between 0.20% and 0.45%. In a preferred embodiment, the second portion has a Δ between 0.4% and 0.45% for all radii between 1 and 1.5 μm. In another preferred embodiment, the second portion has a Δ between 0.2% and 0.35% for all radii between 1.5 and 2.5 μm.

The core also preferably includes a third portion enclosed immediately adjacent to the second portion, which extends to a radius of 4.5 μm and has a Δ between 0.15% and 0.35%. In a preferred embodiment, the third portion has a Δ between 0.2% and 0.3% for all radii between 2.5 and 4.5 μm.

Preferably, the absolute value of the difference in Δ between all the radii in the third part is less than 0.1%.

Preferably, the absolute value of the difference in Δ between all radii between r = 2.5 μm and r = 4.5 μm is less than 0.1%.

The core also preferably comprises a fourth portion enclosed immediately adjacent to the third portion, which extends to a radius of 6 μm and has a Δ between 0.1% and 0.3%. In a preferred embodiment, the fourth portion has a Δ between 0.2% and 0.35% for all radii between 4.5 and 5 μm. In another preferred embodiment, the fourth portion has a Δ between 0.15% and 0.3% for all radii between 5 and 6 μm.

The core segment also preferably includes a fifth portion enclosed immediately adjacent to the fourth portion, which extends to a radius of 9 μm and has a Δ between 0.0% and 0.15%.

In a preferred embodiment, Δ (r = 5.5 μm)> 0.1%. Preferably, Δ (r = 6 μm)> 0%.

In a preferred embodiment, A _L01 and A _L02 are less than 400 μm ² .

In a preferred embodiment, 0.5 <AOEA _L01 / AOEA _L02 <2 and more preferably 0.6 <AOEA _L01 / AOEA _L02 <1.5.

Preferably, the outermost radius r _CORE of the _core is larger than 6 μm, more preferably larger than 6 μm and smaller than 15 μm, more preferably larger than 6 μm and smaller than 12 μm. In a preferred embodiment, r _CORE is between 6 μm and 10 μm.

Preferably, the optical fibers described herein allow for adequate performance in multiple operating wavelength ranges between about 1260 nm and about 1650 nm. More preferably, the optical fibers described herein allow for proper performance at multiple wavelengths from about 1260 nm to about 1650 nm. In a preferred embodiment, the optical fiber described herein is a double window fiber that can accommodate operation in at least a 1310 nm window and a 1550 nm window.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Although the fibers described in US Pat. No. 6,490,396 and US Provisional Application No. 60 / 467,676 are preferred, other fibers may be used. Preferably, the optical fiber for the optical fiber span 20 (including its length) is selected such that the SBS threshold of the fiber satisfies the following inequality (1).

(1)

(One)

이고,

은 m/W 단위로 측정된 브릴루앙 이득 계수이고, 1≤K≤2는 편광 인자, Δυ 및 Δυ _B 는 각각의 브릴루앙 이득의 레이저 소스의 반치전폭(FWHM) 이고, α는 섬유 손실 계수(감쇠)이고, A _eff 는 섬유의 유효 영역이고, 크기가 없는 파라미터 γ _B 는 다음의 수식 (2)의 해답으로 찾아진다.here,

ego,

Is the Brillouin gain factor measured in m / W, 1 ≦ K ≦ 2 is the polarization factor, Δυ and Δυ _B are the full width at half maximum (FWHM) of the laser source of each Brillouin gain, and α is the fiber loss factor ( Damping), A _eff is the effective area of the fiber, and the parameter γ _B without size is found by the solution of the following equation (2).

(2)

(2)

Where L is the fiber length and the constant C is given by the following equation (3).

(3)

(3)

GHz는 스톡스파와 신호파 사이의 주파수 차이다. J. Lightwave Technol .( vol.20, pp. 1635-1643(2002))를 참조하라.Where T is fiber temperature, k is Boltzmann constant, υ _s is signal frequency,

GHz is the frequency difference between the stock wave and the signal wave. J. Lightwave Technol . (vol. 20, pp. 1635-1643 (2002)).

FIG. 3 shows the calculated SBS thresholds for fiber path lengths for optical fibers with different inherent SBS thresholds. The SBS suppression capability of analog sources is commonly cited as a 50 km sample of standard single mode fibers such as Corning SMF-28e® fibers. Such fibers typically have SBS thresholds ranging from about 7 dB with CW narrow linewidth sources to about 17 dBm with strongly dithered sources.

4 shows the reflected power measured as a function of input power for three optical fibers having a length of about 50 km. Curve 5 corresponds to standard single mode fiber. Curves 6 and 7 show an increase in SBS thresholds above the standard single mode of 2.5 and 3.9 dBm, respectively, as described in US Pat. No. 6,490,396 and US Application No. 10 / 818,054.

Preferably, the optical fiber of the trunk fiber optic link 20 has an SBS threshold that is at least 1 dB higher, more preferably at least 2 dB higher, more preferably at least 3 dB higher than the standard single mode fiber. For access / CATV network applications, the preferred fiber has an SBS threshold that is at least 2 dB higher than standard single mode fiber.

Curve 0 in FIG. 3 corresponds to a standard single mode fiber. Curves 1, 2 and 3 in FIG. 3 correspond to fibers 1 dB, 2 dB and 3 dB increased at the SBS threshold of the fiber, respectively, than the standard single mode fiber. 3 shows that an increment of 1 dB in the SBS threshold of the fiber results in an available fiber path length of the trunk fiber link or feed line 20 of 10 km, 14 km and 18 km, respectively, for the same SBS threshold power of 22 dBm.

Operation below the SBS threshold of the optical fiber in the trunk line is preferred. Preferably, the maximum light output power is about 1 dB below the actual SBS threshold of the optical fiber of the trunk line 20. More preferably, the maximum light output power is about 2 dB below the actual SBS threshold of the trunk link 20.

In a first set of preferred embodiments, the optical communication system described herein connects an optical signal source 12 and an optical signal source 12 to a receiver 32 for delivering an optical signal with an input power greater than 16 dBm. An optical signal distribution network comprising an optical fiber span, wherein the longest fiber links 22, 26, 30 included in the fiber path length are greater than 45 km, the signal being a subcarrier multiplexing signal, wherein the system parameter is In the operating wavelength range, when the output power is greater than 16 dBm, for channels in the 45-560 MHz range, the CNR is selected to be greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc.

In all the systems described herein, a method of operating such a system is also conceivable. For example, a method of operating a system according to a first set of preferred embodiments includes inputting a signal from a signal source 12 into an optical fiber span 20, where the optical fiber path length 20 is included. The longest fiber links 22, 26, 30 are greater than 45 km and the signal is a subcarrier multiplexing signal and the system parameter is for a channel in the 45-560 MHz range when the output power is greater than 16 dBm in the operating wavelength range. , CNR is greater than 50dB, CSO is less than -60dBc, and CTB is less than -60dBc.

System parameters include optical fiber characteristics such as output power, signal phase modulation, signal dithering, bitrate and length, attenuation and SBS thresholds.

More preferably, the system parameter indicates that at output power greater than 16 dBm, substantially all channels in the 45-560 MHz range have CNR greater than 50 dB, CSO less than -65 dBc, and CTB less than -65 dBc. Most preferably, at system output power greater than 16 dBm, substantially all channels in the 45-560 MHz range exhibit CNR greater than 52 dB, CSO less than -60 dBc, and CTB less than -60 dBc. In another of the first set of preferred embodiments, the signal source output power is greater than 17 dBm and the system parameter is substantially equal to all channels in the 45-560 MHz range when the output power is greater than 17 dBm in the operating wavelength range. CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc.

In another of the first set of preferred embodiments, the signal source output power is greater than 18 dBm and the system parameter is substantially all channels in the 45-560 MHz range when the output power is greater than 18 dBm in the operating wavelength range. This shows a CNR greater than 50 dB, a CSO less than -60 dBc, and a CTB less than -60 dBc.

The longest fiber link included in the fiber path from the signal source to the first amplifier is preferably greater than 60 km, more preferably greater than 80 km.

In a second set of preferred embodiments, the optical communication system described herein comprises an optical signal source 12 for delivering an optical signal with an input power greater than 16 dBm and an optical fiber connecting the optical signal source 12 to a receiver 32. An optical signal distribution network comprising a span 20, wherein the fiber path length from the optical signal source to the receiver is greater than 50 km, the path length not including an optical amplifier, and the signal being subcarrier multiplexed. Signal, where the system parameter is CNR greater than 50 dB, CSO less than -60 dBc, and CTB greater than -60 dBc, for channels in the 45-560 MHz range when the output power is greater than 16 dBm in the operating wavelength range. It is chosen to be small.

In one of the preferred embodiments of the second set of preferred embodiments, the fiber span 20 path length is greater than about 70 km, more preferably greater than about 80 km, most preferably greater than about 90 km, and the system parameters. In the operating wavelength range, when the output power is greater than 17 dBm, substantially all channels in the 45-560 MHz range represent CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. More preferably, in the operating wavelength range, when the output power is greater than 18 dBm, substantially all channels in the 45-560 MHz range have CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. Indicates. Most preferably, in the operating wavelength range, when the output power is greater than 19 dBm, substantially all channels in the 45-560 MHz range have CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. Indicates.

In a third set of preferred embodiments, the optical communication system described herein comprises an optical signal source 12 for delivering an optical signal with an input power greater than 16 dBm and an optical fiber connecting the optical signal source 12 to a receiver 32. An optical signal distribution network comprising a span 20, wherein the fiber path length from the optical signal source to the receiver is greater than 120 km, wherein the system parameter is greater than 16 dBm in the operating wavelength range. When the channel is in the 45-560 MHz range, the CNR is chosen to be greater than 50 dB, the CSO to be less than -60 dBc, and the CTB to be less than -60 dBc.

In one preferred embodiment of the third set of preferred embodiments, the fiber used in the fiber path comprises a zero dispersion wavelength of less than 140 nm.

The fiber path may include one or more optical amplifiers 24, 28 to further increase the total possible distance between the signal source and the receiver. Preferably, the output power is greater than 18 dBm and the system parameter indicates that in the operating wavelength range, substantially all channels in the 45-560 MHz range are CNR greater than 50 dB, CSO less than -60 dBc and CTB less than -60 dBc. Most preferably, the output power is greater than 20 dBm and the system parameter indicates that in the operating wavelength range, substantially all channels in the 45-560 MHz range have CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. .

In a fourth set of preferred embodiments, the optical communication system described herein comprises an optical signal source 12 for delivering an optical signal with an input power greater than 14 dBm and an optical fiber connecting the optical signal source 12 to a receiver 32. An optical signal distribution network comprising a span 20, wherein the fiber path length from the optical signal source to the receiver is greater than 50 km and the fiber exhibits a zero dispersion wavelength less than 1400 nm, where the system parameters are In the operating wavelength range, when the output power is greater than 14 dBm, for channels in the 45-560 MHz range, the CNR is selected to be greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc.

Advantageously, said output power is greater than 15 dBm and said system parameter exhibits, in the operating wavelength range, substantially all channels in the 45-560 MHz range, CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. . Even more preferably, the output power is greater than 16 dBm and the system parameter is such that in the operating wavelength range, substantially all channels in the 45-560 MHz range are CNR greater than 50 dB, CSO less than -60 dBc and CTB less than -60 dBc. Indicates. Most preferably, the output power is greater than 18 dBm and the system parameter indicates that in the operating wavelength range, substantially all channels in the 45-560 MHz range are CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. .

In a fourth set of preferred embodiments the fiber path length 20 is greater than about 70 km, more preferably greater than about 80 km, and most preferably greater than about 90 km.

In a fifth set of preferred embodiments, the optical communication system described herein comprises an optical signal source 12 for delivering an optical signal with an input power greater than 19 dBm and an optical fiber connecting the optical signal source 12 to a receiver 32. An optical signal distribution network comprising a span 20, wherein the fiber path length from the optical signal source to the receiver is greater than 90 km, and the signal is a subcarrier multiplexing signal, where the system parameter is an operating wavelength. In the range, when the output power is greater than 19 dBm, for channels in the 45-560 MHz range, the CNR is selected to be greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc.

More preferably, the output power is greater than 20 dBm and the system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range have CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. Indicates. Even more preferably, the output power is greater than 21 dBm and the system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range have CNR greater than 50 dB, CSO less than -60 dBc and CTB less than -60 dBc. Indicates. Most preferably, the output power is greater than 22 dBm and the system parameter indicates that in the operating wavelength range, substantially all channels in the 45-560 MHz range are CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. .

For any of the above-mentioned preferred embodiments of all sets, a further preferred embodiment includes an optical signal source comprising a transmitter and an amplifier for amplifying the optical signal generated by the transmitter.

For any of the above-mentioned preferred embodiments of all sets, a further preferred embodiment includes a transmitter for generating an optical signal at multiple wavelengths.

Preferably, at least one optical signal is transmitted at a wavelength in the wavelength range between 1530 nm and 1565 nm. In a preferred embodiment, the optical signal is transmitted at about 1550 nm wavelength. In another preferred embodiment, at least one optical signal is transmitted at a wavelength within a wavelength range between 1460 nm and 1520 nm. In one preferred embodiment, the optical signal is transmitted at a wavelength of about 1490 nm.

It is to be understood that what is described herein is merely an illustration of the invention and is intended to provide an overview for understanding the nature of the invention as defined in the claims. The accompanying drawings are intended to provide further understanding of the invention and are a part of this specification. The drawings, along with the description, illustrate various features and embodiments of the invention provided to illustrate the principles and operation of the invention. It will be apparent to those skilled in the art that various modifications may be made to the preferred embodiments of the invention described herein without departing from the spirit and scope of the invention as defined in the appended claims. Will be obvious.

Claims (33)

In the optical communication system, An optical signal source for delivering an optical signal with an input power greater than 16 dBm; And An optical signal distribution network comprising an optical fiber of a predetermined length connecting the optical signal source to a receiver, Wherein the longest fiber link included in the fiber path length from the optical signal source to the receiver, connecting one of the transmitter, amplifier or receiver to the other of the transmitter, amplifier or receiver, is greater than 45 km and the signal is a subcarrier A multiplexing signal, wherein the parameter of the system is that, in the operating wavelength range, when the output power is greater than 16 dBm, for a channel in the 45-560 MHz range, the CNR is greater than 50 dB, the CSO is less than -60 dBc, and the CTB Is selected to be less than -60 dBc. The method of claim 1, Substantially all channels within the 45-560 MHz range exhibit a CNR greater than 50 dB, a CSO less than -65 dBc, and a CTB less than -65 dBc, at an output power greater than 16 dBm. The method of claim 1, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 52 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 16 dBm. Optical communication system, characterized in that selected. The method of claim 1, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 17 dBm. Optical communication system, characterized in that selected. The method of claim 1, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 18 dBm. Optical communication system, characterized in that selected. The method of claim 1, And the longest fiber link included in the fiber path length from the optical signal source to the first amplifier is greater than 60 km. The method of claim 1, And the longest fiber link included in the fiber path length from the optical signal source to the first amplifier is greater than 60 km. In the optical communication system, An optical signal source for delivering an optical signal with an input power greater than 16 dBm; And An optical signal distribution network comprising an optical fiber of a predetermined length connecting the optical signal source to a receiver, Wherein the fiber path length from the optical signal source to the receiver is greater than 50 km, the path length does not include an optical amplifier, and the signal is a subcarrier multiplexing signal, wherein the parameter of the system is an operating wavelength range Wherein, when the output power is greater than 16 dBm, for a channel in the 45-560 MHz range, the CNR is selected to be greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. The method of claim 8, And the fiber path length is greater than about 70 km. The method of claim 8, And the fiber path length is greater than about 80 km. The method of claim 8, And the fiber path length is greater than about 90 km. The method of claim 8, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 17 dBm. Optical communication system, characterized in that selected. The method of claim 8, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 18 dBm. Optical communication system, characterized in that selected. The method of claim 8, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 19 dBm. Optical communication system, characterized in that selected. In the optical communication system, An optical signal source for delivering an optical signal with an input power greater than 16 dBm; And An optical signal distribution network comprising an optical fiber of a predetermined length connecting the optical signal source to a receiver, Wherein the fiber path length from the optical signal source to the receiver is greater than 120 km, wherein the parameter of the system is in the operating wavelength range for a channel in the 45-560 MHz range when the output power is greater than 16 dBm. And wherein the CNR is greater than 50 dB, the CSO is less than -60 dBc, and the CTB is less than -60 dBc. The method of claim 15, And wherein the fiber used in the fiber path comprises a zero dispersion wavelength of less than 1400 nm. The method of claim 15, And the fiber path comprises at least one optical amplifier. The method of claim 15, And the fiber path comprises at least two optical amplifiers. The method of claim 15, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 18 dBm. Optical communication system, characterized in that selected. The method of claim 15, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 20 dBm. Optical communication system, characterized in that selected. In the optical communication system, An optical signal source for delivering an optical signal with an input power greater than 14 dBm; And An optical signal distribution network comprising an optical fiber of a predetermined length connecting the optical signal source to a receiver, Wherein the fiber path length from the optical signal source to the receiver is greater than 50 km and the fiber exhibits a zero dispersion wavelength of less than 1400 nm, wherein the parameter of the system is that the output power is greater than 14 dBm in the operating wavelength range. When large, for channels in the 45-560 MHz range, the CNR is selected to be greater than 50 dB, the CSO to be less than -60 dBc, and the CTB to be less than -60 dBc. The method of claim 21, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 15 dBm. Optical communication system, characterized in that selected. The method of claim 21, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 16 dBm. Optical communication system, characterized in that selected. The method of claim 21, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 18 dBm. Optical communication system, characterized in that selected. The method of claim 21, And the fiber path length is greater than about 70 km. The method of claim 21, And the fiber path length is greater than about 80 km. The method of claim 21, And the fiber path length is greater than about 90 km. In the optical communication system, An optical signal source for delivering an optical signal with an input power greater than 19 dBm; And An optical signal distribution network comprising an optical fiber of a predetermined length connecting the optical signal source to a receiver, Wherein the fiber path length from the optical signal source to the receiver is greater than 90 km and the signal is a subcarrier multiplexing signal, where the parameter of the system is greater than 19 dBm in the operating wavelength range, For channels in the 45-560 MHz range, the optical communication system is selected such that the CNR is greater than 50 dB, the CSO is less than -60 dBc, and the CTB is less than -60 dBc. The method of claim 28, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 20 dBm. Optical communication system, characterized in that selected. The method of claim 28, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 21 dBm. Optical communication system, characterized in that selected. The method of claim 28, The system parameter is such that, in the operating wavelength range, substantially all channels in the 45-560 MHz range exhibit CNR greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc, at an output power greater than 22 dBm. Optical communication system, characterized in that selected. In the optical communication system, An optical signal source for delivering an optical signal with an input power greater than 14 dBm; And An optical signal distribution network comprising an optical fiber of a predetermined length connecting the optical signal source to a receiver, Here, the fiber indicates a smaller first acousto-optic effective area AOEA _L01 and smaller second acousto-optic effective area AOEA _L02 that are more than ^two 140㎛ 140㎛ ^2, the group the first and second acousto-optic effective area is the Measured at the Brillouin frequency of the optical fiber, the fiber path length from the optical signal source to the first amplifier is greater than 45 km, and the signal is a subcarrier multiplexing signal, wherein the parameters of the system are output in the operating wavelength range. When the power is greater than 16 dBm, for a channel in the 45-560 MHz range, the CNR is selected to be greater than 50 dB, CSO less than -60 dBc, and CTB less than -60 dBc. The method of claim 32, The relationship between the L01 and L02 acoustic effective area of the fiber is 0.4 <AOEA _L01 / AOEA _L02 <2.5.

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